FTSE 100 bosses are preparing to provide last-minute backing for a Remain vote ahead of this week's referendum.
Remain campaigners are this week preparing to publish a letter from chief executives lending their support to the EU.
City A.M. understands that signatories will include RSA chief executive Stephen Hester, while the Sunday Times has reported that Barclays chairman John McFarlane has also signed up.
Barclays and RSA declined to comment.
The letter is being co-ordinated by Britain Stronger in Europe's Gabe Winn, who previously ran communications for British Gas parent, and FTSE 100 member, Centrica Energy.
A spokesman for Britain Stronger in Europe said: “The campaign to keep Britain in Europe’s 500m-strong free trade single market has been backed by the vast majority of businesses, large and small.
“We are confident more and more businesspeople will continue to speak out in the final days of this campaign to say that being in creates jobs, boosts trade, and attracts investment.”
Business leaders stress in the letter that EU membership is good for business and jobs.
It comes after James Dyson lent his support to the Leave campaign. Dyson, who has long been a critic of UK immigration rules, argued that EU membership restricted the ability of employers to recruit high quality staff from other parts of the world.